Abstract Background/Rationale: Obesity has reached epidemic proportions, and often has serious adverse health consequences. The VA has been deploying a "MOVE! Weight Management Program" nationally in the general veteran population. Since individuals with serious mental illness (SMI) usually have cognitive problems, specialized psychoeducational interventions are required in this population. Specialized psychoeducational interventions for weight have been developed and studied in populations with SMI. This evidence-based practice has been adapted for use in VA, resulting in a "MOVE! SMI" intervention. However, it has proven to be quite difficult to disseminate this intervention. Patients with SMI often have limited transportation options, and may not want to participate in groups. Also, in-person MOVE! SMI requires substantial time from mental health clinicians. This clinician time has been difficult to redeploy or not available at many VA locations. It is very likely that these barriers can be addressed with a computerized, web-based version of MOVE! that is tailored for veterans with SMI. Specialized web-based approaches have been studied and found to be successful in this population, and can deliver content that is intensive and engaging with minimal requirements for staff time. Objectives: The VISN 5 and 22 MIRECCs have developed a prototype web-based system that provides computerized counseling regarding diet to veterans with SMI. The proposed project will expand this system. This project's objectives are to: 1) develop a comprehensive web-based system that delivers MOVE! using design features that meet the needs of individuals with SMI;2) evaluate the effectiveness, in veterans with SMI, of web-based MOVE! compared with in-person MOVE! and a control group;and, 3) characterize, from the patient's perspective, the strengths, weaknesses, and barriers to the use of in-person and web-based MOVE!. Methods: This is a prospective, randomized, controlled trial in 300 veterans with SMI who are overweight and receiving treatment with medications that often have weight gain as a major side-effect. Participants are assigned to in-person MOVE! SMI, web-based MOVE! SMI, or a control group. Research assessments occur at 0, 3, and 6 months. Changes in outcomes are compared over time between the three groups. Significance: By losing weight, veterans with SMI can decrease their risk for medical problems that have a serious negative effect on their quality of life and life expectancy. A web-based system that helps veterans lose weight could be feasible to disseminate broadly at VA sites, including medical centers and community based outpatient clinics serving both rural and urban areas.